1. Field of the Invention
In one of its aspects, the present invention relates to an attachment device, preferably to a trim cover attachment device. In another of its aspects, the present invention relates to a resilient device, preferably a foam device in a vehicular seat, incorporating the present attachment device, preferably for attachment of a trim cover to the foam device. In yet another of its aspects, the present invention provides a process for producing a resilient device, preferably a foam device in a vehicular seat, incorporating the present attachment device, more preferably a trim cover attachment device. In yet another of its aspects, the present invention provides a mold for producing a resilient device, preferably a foam device in a vehicular seat, incorporating the present attachment device, preferably for attachment of a trim cover to the foam device.
2. Description of the Prior Art
Attachment of a trim cover to a resilient device is generally known.
In most cases, the resilient device is a foam device, although, in some cases, a fibrous matrix such as rubberized horsehair and the like is still being employed. Typically, it is desired to secure a trim cover to a resilient device to produce a vehicular seat or a component of a vehicular seat.
There are three general categories of approaches in attachment of a trim cover to a resilient device: adhesive, foam-in-place and mechanical. The present invention relates to an improvement falling in the latter category and thus, prior art in this category will be discussed.
In the mechanical approach for attachment of a trim cover to a resilient device, there are (at least) four sub-categories. For ease of description, reference will be made to a foam device.
First, it is known in art to employ so-called “hog-rings” to secure a trim cover to a resilient device. In this approach, a metal wire is melded into the so-called A-surface of the foam device. The metal wire is exposed at selected spots, typically in a trench, on the surface of the foam device. A trim cover is provided and has a finished outer surface made of leather, cloth, vinyl or the like. Commonly attached to the underside of the trim cover is a non-woven material, a felt material and the like. A hard plastic (or other) bead is attached to the non-woven material. Of course other methods are attaching the hard plastic bead to the trim cover are used in the art. The trim cover is attached to the foam device by aligning the metal wire in the foam device with the hard plastic bead in the trim cover and thereafter engaging the two with a metal ring. Typically, the metal ring is deployed from a so-called hog-ring gun. This approach has been used for many years to secure a trim cover to a foam device. This approach suffers from a number drawbacks. For example, a significant capital cost is required to acquire the hog-ring gun and a significant associated labour cost is required to ensure that trim covers can be attached to foam devices at a rate commensurate with the rate at which the foam device is being produced. Further, since deployment of the first hog-ring immovably secures the trim cover to foam device, there is no play or give. The result of this is that perfect placement of trim cover over the foam device must be achieved prior to deployment of the first hog ring to avoid significant loss of efficiency. Still further, this approach is difficult to use reliably when producing a vehicular seat product which incorporates one or more of a seat heater and an occupant detection system. Still further, the use of metal in the foam device creates additional cost in recycling the finished product after complete of its life cycle. A modification of this approach is to replace the metal wire typically molded into the A-surface of the foam device with a mounting device made of foam—see, for example, Canada patent application 2,165,930 [Grund et al.], published on Jun. 24, 1996 and DE 44 46 450 C1 [Johnson Controls GmbH & Co.], granted Apr. 4, 1996. Another modification of this approach is to utilize a mechanical clip to connect the trim cover to the metal wire molded into the A-surface of the foam device—see, for example DE 195 30 379 C2 [Johnson Controls GmbH & Co.], published Dec. 19, 1996.
Second it is known to utilize a plurality of independent or single mechanical clips to secure the trim cover to the foam device. In this approach, a series of mechanical clips is molded in the A-surface of the foam device. Each mechanical clip typically comprises a base which is molded into the foam and a receptacle or clip portion which emerges from the foam at selected locations on the A-surface of the foam device. See, for example, one or more of the following prior art references:                DE 299 17 372 U1 [Johnson Controls GmBH & Co.], published Feb. 24, 2000; and        DE 298 21 697 U1 [Bertrand Faure Sitztechnik GmbH & Co.], published Mar. 25, 1999.For a typical vehicular seat component (e.g., a seat bottom or a seat back), it is common to require 12-30 of these clips to be molded into the foam device. This approach suffers from a number of drawbacks. For example, it is very difficult to achieve optimal alignment of the individual clips using this approach. This results in production of an unsightly product. Further, this approach requires significant time to correctly dispose the individual clips in the mold. This results in one or both of low efficiency and increased labour.        
Third, it is known to use so-called Velcro™-type fasteners to attach a trim cover to a foam device. These fasteners are also known in the art as touch fasteners or “hook and loop” fasteners. While this approach is reliable, it does suffer from a number of drawbacks. For example, the this type of fastener is generally regarded one of the most expensive approaches to utilize to secure a trim cover to a foam device. Further, this approach is not well suited to fastening around a curve portion of the foam device without incurring significant wastage. Third, in many applications, the use of this approach necessitates the use of a wide fastener to achieve sufficient pullout strength. The result of this is a relatively wide trench which results in a relatively unsightly product.
Fourth, from U.S. Pat. No. 5,641,552 [Tillner], it is known to utilize an anchoring strip which is molded in A-surface of the foam device. The anchoring strip is in the form a wide, flat connecting bar made of a molded plastic body (polypropylene is provided as an example) and having a series of C-clips disposed at various spots along its length. The wide, flat connecting bar is described as being flexible perpendicular to its main plane. It is clear that this is the only moment of flexibility of the wide, flat connecting bar. This approach has a number of drawbacks. For example, the anchoring strip is not well suited to being used around corners and, for most cost-efficient applications, is really only applicable in straight lengths. Further, if the final product is a vehicle seat, the use of a wide, flat connecting bar made of plastic deleteriously affects comfort. Still further, demolding a foam part having a wide, flat connecting bar of this an anchoring strip is difficult to achieve reliably without tearing out of a portion of the anchoring bar from the A-surface of the foam part. Still further, it is impractical and, in most cases, not possible, to mold the anchoring strip in to foam without fouling of the C-clips.
British patent application 2,238,708A [White] teaches a device for attaching material to a seat in a manner similar to the device taught by Tillner. The device is in the form of a rail having one or more clip members which form an open loop. A flat vertical connecting portion is interposed between the rail and the one or more clip members such that the clip portion and the rail are remote from one another. This approach has a number of drawbacks. First, the device taught by White is not easily useable in a commercial setting due to the fact that there is no place on the rail which provides a convenient press point for insertion of the device in a mold. In fact, White is completely silent on how the device is to be used in a mold or on a mold therefore. This disadvantage is exacerbated by the presence of the flat vertical connecting portion between the rail and the one or more clip members rendering the device cumbersome to insert in a mold. Second, the distance between the rail and the clip member(s) is too large to allow the device to be conveniently used in a process and to allow the device to be molded into many conventional dimensioned foam elements. On the latter point, for example, in a conventional vehicular seat, the thickness of the seat in the location of the trenches is about 20 to about 25 mm. This dimension renders the device taught virtually unusable as taught by White.
Thus, despite the advances made to date, there is still room for improvement. Specifically, it would be advantageous to have an attachment device which obviates or mitigates and least one of the above-mentioned drawbacks of the prior art. It would be particularly advantages if the attachment device was not only well suited for attachment of a trim cover to a resilient body but could also be use to attach other elements to the resilient body.